Leak detection system comprising a tracer gas mediating unit

ABSTRACT

A system for detection of a leak at a leakage testing point of a test object by a tracer gas. A positionable tracer gas mediating unit has a tip. A marker is attachable at the leakage testing point. A marker detector is associated with the positionable tracer gas mediating unit. The tip of the tracer gas mediating unit is arranged to be positioned within a predetermined distance interval from the marker during a leak detection test. The marker detector is arranged to detect the marker when the tip is positioned within the predetermined distance interval so as to certify a correct positioning of the tip.

TECHNICAL FIELD

The present invention relates to a system for detection of a leak at aleakage testing point of a test object by means of a tracer gas, whichsystem comprises a positionable tracer gas mediating unit having a tip.

BACKGROUND OF THE INVENTION

The leak tightness of an object may be necessary or desired to determinefor different reasons. For example, it may be necessary to test the leaktightness of a product in order to guarantee a certain quality of theproduct, or to test the leak tightness of a product or industrialfacilities due to environmental concern. Typical examples of productsrequired to be tested for leakage are parts of refrigeration systems forindustrial, commercial, domestic and automotive use as well as liquidand gas carrying parts in the automotive industry, such as for examplefuel tanks and aluminium wheels.

Today there are many known systems and methods for performing leaktesting of an object. Some of them are based on tracer gas techniques,whereby the presence of a tracer gas is utilized for detecting leaks.The tracer gas, or a gas mixture comprising the tracer gas, is thendetected after leak passage by means of a detecting instrument. Examplesof commonly utilized tracer gases are helium, hydrogen, refrigerants,sulfur hexafluoride and carbon dioxide.

One tracer gas method for performing leak testing of an object is theso-called sniffing method. In the sniffing method, the test object ispressurized with a tracer gas. Tracer gas leaking out of the object isdetected by tracer gas detecting equipment comprising a sniffer probewith a sniffer tip and a tracer gas sensor. The sniffer probe picks upany tracer gas that has leaked out of the test object by means of thesniffer tip and mediates the tracer gas to the tracer gas sensor.

Another tracer gas method for performing leak testing of an object isthe so-called spraying method. In the spraying method, the test objectis under vacuum and the interior of the test object is connected to atracer gas detecting equipment comprising a tracer gas sensor. Tracergas is sprayed onto the test object on the outside thereof by means of atracer gas spraying device with a spraying tip, i.e. tracer gas ismediated from a tracer gas source by means of the spraying tip onto theoutside of the test object. Any tracer gas that enters the test objectis then detected by means of the tracer gas detecting equipment.

Both the sniffing method and the spraying method may be applied forlocal leak detection, i.e. leak detection at a specific leakage testingpoint. Local leak detection may also be called pin pointing. In localleak detection, the sniffer tip and the spraying tip, respectively, arepositioned at a leakage testing point of the object in order to test theleak tightness of that specific leakage testing point. However, in orderfor the sniffing method and the spraying method, respectively, to bereliable when they are applied for local leak detection, the sniffer tipand the spraying tip, respectively, have to be positioned within apredetermined distance interval from the leakage testing point. In casea sniffer tip or spraying tip, respectively, is not positioned withinthe correct distance interval from the leakage testing point, the tipmight not be able to pick up or spray, respectively, the tracer gas in acorrect way. Incorrect test results may then be obtained. The testedobjected may then be determined as leak tight in spite of the fact thatthere is a leak or may be determined as having a smaller leak than itactually has. Thus, the test object may then be determined to be “OK”even though it is not according to the requirements of the test.

The predetermined distance interval depends on the many differentfactors. For example, it depends on properties of the utilized tracergas, and the sensitivity of the sensor and/or the detecting equipmentfor the actual tracer gas. In addition, the predetermined distanceinterval depends on which size of leaks that it is desired to detect. Ifit is desired to detect small leaks of a test object, the predetermineddistance interval is shorter than if it is desired to detect largerleaks of the test object.

One way to avoid the risk of placing the sniffer tip and the sprayingtip, respectively, at an incorrect distance from the leakage testingpoint is to perform a so-called global leak detection instead of a localleak detection. Both the sniffing method and the spraying method may beapplied for global leak detection. In global leak detection, the testobject is placed in a cabinet or test chamber, whereby it is testedwhether the test object is leaking at any point or is leak tight, i.e.it is not tested whether there is a leak at a specific testing point,but the “total” leakage of the test object is tested. In case thesniffing method is utilized, the sniffer tip is positioned in the testchamber and any increase of the tracer gas concentration in the testchamber is detected. In case the spraying method is utilized, thespraying tip sprays tracer gas into the test chamber in order tosurround the complete test object and any increase of the tracer gasconcentration in the test object is detected. However, the global leakdetection is not suitable to utilize for all types of test objects. Morespecifically, it is neither efficient nor cost effective when the testobject is complex or has such dimensions that it is necessary to utilizea big or complex test chamber. Since many test objects have a complexdesign, local leak detection is commonly utilized.

One device which may be utilized in local leak detection and whichcomprises means for avoiding the risk of placing a sniffer tip at anincorrect distance from a test object is described in WO 2006/069877.More specifically, WO 2006/069877 describes a leak detector comprising asniffer probe with a sniffer tip. The sniffer probe is provided with adistance detector for determining the distance between the sniffer tipand a test object. A leak detection test is only initiated if thedistance between the sniffer tip and the test object corresponds to apredetermined value, whereby measurement errors due to placement of thesniffer tip at an incorrect distance from the test object are avoided.In a preferred embodiment, the distance detector is an optical detector,which comprises a light emitting device and a light receiving device.The light emitting device projects light onto a point on the test objectand the light receiving device measures the intensity of the reflectedlight, whereby the distance between the sniffer tip and the test objectis determined.

Thus, the leak detector described in WO 2006/069877 may be utilized toassure that the sniffer tip is positioned at a correct distance from thetest object during a leak detection test. However, it may only beutilized to assure that the sniffer tip is positioned within a correctdistance from the test object, not to assure that the sniffer tip isdirected towards the correct testing point. This means that when theleak detector described in WO 2006/069877 is utilized, any point on thetest object may be interpreted as the correct testing point if thedistance between the point and the sniffer tip is correct. In otherwords, when utilizing the leak detector described in WO 2006/069877 theoperator may direct the sniffer tip towards a point on the test objectwhich is thought to be the correct testing point, but which is not. Thenthe leak test is performed at a correct distance from the test object,but at an erroneous point on the test object. The fact that an operatormay direct the sniffer tip towards an erroneous point on the test objectmay be due to various facts. For example, many test objects are complexand many leakage test procedures are performed under poor lighting,whereby it may be difficult to see the intended testing point.

In view of the above, utilization of the leak detector described in WO2006/069877 implies that the operator knows exactly where the leakagetesting point is located on the test object and that the operatordirects the sniffer tip towards that point. It is, thus, highly operatordependent, i.e. it is dependent on the behavior of the operator. Inaddition, the utilization of the leak detector described in WO2006/069877 is also dependent on the properties of the surface of thetest object.

Thus, there is still a need for a system for detection of a leak at aleakage testing point (i.e. which may be utilized for local leakdetection), whereby the above mentioned drawbacks are avoided.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide animproved system for detection of a leak at a leakage testing point of atest object by means of a tracer gas, which system comprises apositionable tracer gas mediating unit having a tip.

This object is achieved in accordance with the characterizing portion ofclaim 1.

Preferred embodiments are listed in the dependent claims.

Still other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference characters denote similarelements throughout the several views:

FIG. 1 shows a schematic view of a first embodiment of a systemaccording to the invention applied on a test object;

FIG. 2 shows a schematic view of a second embodiment of the systemaccording to the invention applied on a test object;

FIG. 3 shows a schematic view of a third embodiment of the systemaccording to the invention applied on a test object; and

FIG. 4 shows a schematic view of a fourth embodiment of the systemaccording to the invention applied on a test object.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides a system that may be utilized fordetection of a leak at a leakage testing point of a test object by meansof a tracer gas, i.e. it may be utilized for local leak detection asabove described. The term “leakage testing point” is herein intended tomean a point on an object at which leakage is intended to be tested. Theterm “test object” is herein intended to mean an object which isintended to be tested for leakage and may be, for example, a product oran installation. Examples of products that may be tested for leakage bymeans of the system according to the invention are parts ofrefrigeration systems for industrial, commercial, domestic andautomotive use as well as liquid and gas carrying parts in theautomotive industry, such as for example fuel tanks and aluminiumwheels. The term “tracer gas” is herein intended to mean a gas that isutilized to detect a leak on a test object, i.e. a gas which is detectedafter leak passage. The tracer gas may be a gas that is only utilizedfor test purposes, i.e. a gas that is applied to the test object only inorder to detect any leak, or may be a gas that is a normal component ofthe test object. For example, the tracer gas may be helium, hydrogen,refrigerants, sulfur hexafluoride or carbon dioxide. The term “tracergas mediating unit” is herein intended to mean a unit that mediatestracer gas from the outside thereof into the interior of the unit, or aunit that mediates tracer gas from its interior to the outside thereof.More specifically, the term “tracer gas mediating unit” is hereinintended to mean a sniffer probe or a tracer gas spraying device. Thesniffer probe mediates tracer gas from the outside thereof, i.e. fromthe outside of a test object, into the interior of the sniffer probe.The tracer gas spraying device mediates tracer gas from its interior tothe outside of the spraying device, i.e. to the outside of a testobject. In some embodiments of the system according to the invention, itis designed to be utilized in the above described sniffing method and inother embodiments it is designed to be utilized in the above describedspraying method. Different embodiments of the system according to theinvention will now be described in more detail with reference to thedrawings.

FIG. 1 shows a schematic view of a first embodiment of a system 1according to the invention, by which a leak at a leakage testing point 2of a test object 3 may be detected by means of a tracer gas. The firstembodiment of the system 1 is designed to be utilized in the sniffingmethod and comprises a sniffer probe 4 having a sniffer tip 5. As shownin FIG. 1, the sniffer probe 4 may have a gun-like design. However, itmay have any suitable shape. Tracer gas is schematically illustrated inFIG. 1 in the form of dots.

As above described, the test object 3 is pressurized with a tracer gasin the sniffing method and tracer gas leaking out of the test object 3is detected. The sniffer probe 4 is arranged to pick up any tracer gasthat has leaked out of the test object 3 by means of the sniffer tip 5.More specifically, the sniffer tip 5 comprises a gas inlet orifice 6arranged to mediate tracer gas from the outside of the test object 3into the interior of the sniffer probe 4. Furthermore, the sniffer probe4 is arranged to mediate the tracer gas not only to the interior of thesniffer probe 4, but also to a tracer gas sensor (not shown in FIG. 1).The tracer gas sensor may be located in the sniffer probe 4 or within aseparate unit to which the sniffer probe 4 is connectable. In case thetracer gas sensor is located in the sniffer probe 4, it may either belocated at the sniffer tip 5 or in the remainder of the sniffer probe 4.Due to its tracer gas mediating properties, the sniffer probe 4 isherein denoted as a tracer gas mediating unit.

Furthermore, the sniffer probe 4 is positionable, i.e. it may be movedin order to position the sniffer tip 5 at a certain location in relationto the test object 3. The sniffer probe 4 may be a hand-held unitintended to be manually operated or may be a unit intended to beattached to and manipulated by a robot.

The system 1 according to the first embodiment of the inventioncomprises further a marker 7, which is attachable at the leakage testingpoint 2 of the test object 3. For purposes of illustration, the marker 7is shown as star-shaped. However, it may have any suitable shape. Themarker 7 is intended to be utilized for marking the location of theleakage testing point 2, i.e. it is intended to be utilized as a guideto where the leakage testing point 2 is located. Thus, the marker 7 maybe intended to be attached on the test object 3 as close to the leakagetesting point 2 as possible without disturbing any leakage of tracer gasfrom the interior of the test object 3 to the outside thereof.Furthermore, the marker 7 may be positioned at the leakage testing point2 during manufacture of the test object 3, or after manufacture of thetest object 3 but before leak detection. In case the test object 3comprises two components that are to be assembled, such as two tubecomponents, the marker 7 may either be attached to one of the componentsafter the assembly at an assembly zone or may be attached to one of thecomponents before the assembly at a part intended to be positioned in anassembly zone.

In an alternative, the marker 7 may be intended to be attached on afixture instead of on the test object. The marker 7 is then intended tobe attached on the fixture as close to the leakage testing point 2 aspossible without disturbing any leakage of tracer gas from the interiorof the test object 3 to the outside thereof. This will be furtherdescribed below.

In addition, the system 1 according to the first embodiment of theinvention comprises a marker detector 8, which is associated with thesniffer probe 4. As shown in FIG. 1, the marker detector 8 may bepositioned on the outside of the sniffer probe 4. Alternatively, themarker detector 8 may be positioned within the sniffer probe 4, i.e.either at the sniffer tip 5 or within the remainder of the sniffer probe4.

Furthermore, the sniffer tip 5 is arranged to be positioned within apredetermined distance interval from the marker 7 during a leakdetection test in order to provide reliable test results. In order tocertify a correct positioning of the sniffer tip 5 within thepredetermined distance interval, the marker detector 8 is arranged todetect the marker 7 when the sniffer tip 5 is positioned within thepredetermined distance interval.

For example, the marker detector 8 may generate a signal when thesniffer tip 5 is positioned within the predetermined distance intervalor may be connected to a signal generator which generates a signal whenthe sniffer tip 5 is positioned within the predetermined distanceinterval. The generated signal may be utilized to alert the user, or therobot, that the sniffer tip 5 is correctly positioned in order to starta test. Alternatively, the generated signal may be required in order forthe system 1 to be able to start a test.

Thus, by means of the marker 7 and the marker detector 8 of the system 1according to the invention, it may be assured that the sniffer tip 5 ispositioned within a certain predetermined distance interval from themarker 7. Since the marker 7 is intended to be attached as close to theleakage testing point 2 as possible, it may thereby be assured that thesniffer tip 5 is positioned within a specific distance interval from theleakage testing point 2.

As mentioned above, the sniffer tip 5 has to be positioned within aspecific distance interval from the leakage testing point 2 in order forthe leak detection to be reliable. In case the sniffer tip 5 is notpositioned within a specific distance interval from the leakage testingpoint 2, incorrect results of a leak test may be obtained. According tothe above, this may be avoided by means of the marker 7 and markerdetector 8 according to the invention.

The detection of the marker 7 by the marker detector 8 may be based onany suitable physical principle. The marker 7 and the marker detector 8may be of any suitable types for the application according to theinvention. However, the marker 7 must be possible to attach on the testobject 3 close to the leakage testing point 2. Alternatively, the marker7 must be possible to attach on a fixture close to the leakagemeasurement point 2. The marker detector 8 must be able to detect themarker 7 when the sniffer tip 5 is positioned within the predetermineddistance interval.

For example, the marker 7 may comprise a radio frequency (RF) tag, aradio frequency identification (RFID) tag, a light reflecting componentor a magnetic ink.

RFID is a known technology in which the electromagnetic or electrostaticcoupling in the RF portion of the electromagnetic spectrum is used totransmit signals. An RFID tag comprises typically a device, e.g. amicrochip, which stores information. For example, the microchip mayinclude a unique serial number, but it may also include otherinformation. A reader, or interrogator, communicates with the RFID tagthrough radio waves. The microchip is attached to an antenna thatreceives signals from and sends signals to the interrogator.Furthermore, RFID tags can be active tags, passive tags or semi-passivetags. Active tags include a power source that powers the microchip'scircuitry and transmits a signal to the interrogator. Passive tags donot include a power source. Passive tags draw the power required for thecircuitry and the transmission of information from the electromagneticfield generated by the interrogator. Semi-passive tags are similar toactive tags; however the power source is used to run the microchip'scircuitry, but not to communicate with the interrogator.

In case the marker 7 comprises an RF tag or an RFID tag, the markerdetector 8 comprises a reader which is arranged to detect the tag basedon radio waves, i.e. it communicates with the tag through radio waves.Furthermore, the RFID tag may be an active tag, a passive tag or asemi-passive tag. For example, the RFID tag may be any one of the knownRFID tags that may be utilized for identity determination. The tags maybe configured to only provide a response to the reader when the readeris positioned within an appropriate distance range from the tag. Thus,in case the marker 7 comprises an RF tag or an RFID tag and the markerdetector 8 is a reader for such a tag, the tag may be configured to onlyprovide a response to the marker detector 8 when the marker detector 8is positioned within a certain distance range from the tag. Thereby, themarker detector 8 may be arranged to detect the tag when it ispositioned within the certain distance range from the tag. By adaptingthat certain distance range to the predetermined distance interval, inwhich the sniffer tip 5 is arranged to be positioned during a leakdetection test, the marker detector 8 may be arranged to detect the tagwhen the sniffer tip 5 is positioned within the predetermined distanceinterval.

As mentioned above, the marker 7 may alternatively comprise a lightreflecting component. The light reflecting component is then a componenthaving light reflecting properties, which substantially differ from thelight reflecting properties of the surface of the test object 3 in atleast an area around the leakage testing point 2.

In case the marker 7 comprises a light reflecting component, the markerdetector 8 comprises a light emitting device and a light receivingdevice. Any known suitable light emitting and light receiving devicesfor distance measurements based on measurement of the intensity ofreflected light may be utilized. For example, the light emitting devicemay be a laser source, such as e.g. a pulsed laser. The light receivingdevice may then be a photo detector. By measuring the distance betweenthe marker detector 8 and the light reflecting component based on lightreflection, the distance between the sniffer tip 5 and the lightreflecting component may, thus, be determined. Thereby, the markerdetector 8 may be configured to only detect the marker 7 when thesniffer tip 5 is positioned within the predetermined distance intervalfrom the marker 7.

In a further alternative, the marker 7 comprises a magnetic ink. Thenthe marker detector 8 comprises a magnetic ink reader, which is arrangedto detect the magnetic ink based on magnetic field intensity. Any knownsuitable magnetic ink and magnetic ink reader may be utilized. Bymeasuring the magnetic field intensity, which corresponds to a certaindistance between the magnetic ink reader and the magnetic ink, thedistance between sniffer tip 5 and the magnetic ink may, thus, bedetermined. Thereby, the marker detector 8 may be configured to onlydetect the magnetic ink, i.e. the marker, when the sniffer tip 5 ispositioned within the predetermined distance interval from the marker 7.

Optionally, the marker 7 may further comprise means for recording theresult of the test in the marker 7. Then the test result is immediatelyassociated with the marker 7 and, thus, the leakage testing point 2.Furthermore, the test result may then be stored for later utilizationand there is then no risk of mixing the test results for differentleakage testing points with each other.

Furthermore, in case the marker 7 comprises identifying information,i.e. unique information identifying the marker, the test result may beimmediately associated with the identifying information. This may eitherbe achieved by storing the test result in the marker, or by recordingthe test result together with the identity information in a recordingunit to which the sniffer probe 4 is connectable. For example, RFID tagscomprise identity information.

In a further alternative, the marker 7 comprises a first component,which may be detected by the marker detector 8 for certifying thecorrect positioning of the sniffer tip 5, and a second componentcomprising identity information. The first component may then be an RFtag, an RFID tag, a light reflecting component or a magnetic ink, andthe second component may then be an RFID tag. Optionally, the system 1may then also comprise means for reading the identity information.

Furthermore, the marker 7 and the marker detector 8 of the system 1according to the invention enable not only the assurance that thesniffer tip 5 is positioned within a certain distance interval from theleakage testing point, but also that the leak detection really isperformed at the intended leakage testing point. By means of the marker7, which is intended to be positioned as close to the leakage testingpoint 2 as possible, and the marker detector 8, it may be assured thatthe sniffer tip 5 is directed towards the correct point on the testobject 3 and that the sniffer tip 5 is positioned within thepredetermined distance interval from that point during a leak detectiontest. If the sniffer tip 5 is not directed towards the correct pointand/or if the sniffer tip 5 is not positioned within the correctdistance interval from that point, the marker 7 is not detected, wherebythe operator knows that the sniffer tip 5 is not correctly positioned.In addition, the system may be configured such that a test is notpossible to perform without correct positioning. Thereby, the operatordependency is substantially reduced. Furthermore, the system allowscontrol of the work performed by an operator.

Furthermore, by means of the marker 7 and the marker detector 8, theleakage testing point 2 is automatically identified and it isautomatically assured that the sniffer tip 5 is positioned within aspecific distance interval from the leakage testing point 2, i.e. thesystem itself identifies the leakage testing point and the positioningof the sniffer tip within the correct distance interval. This may alsoimply that the time required for leak testing of the test object 3 issubstantially reduced.

FIG. 2 shows a schematic view of a second embodiment of the system 1according to the invention, which comprises the sniffer probe 4, themarker 7 and the marker detector 8 of the first embodiment of the system1. However, the second embodiment of the system 1 comprises further atracer gas supplying device 9, which is arranged to be utilized forsupplying tracer gas into the test object 3 in order to pressurize thetest object 3 therewith. The tracer gas supplying device 9 may compriseat least one component from the group of a tracer gas source, a gascontroller, a gas pressure regulator and means for connecting the tracergas source to the test object 3. The tracer gas source is arranged toconstitute a source of tracer gas and may be of any suitable type. Thegas controller is arranged to administrate the filling of tracer gasfrom the tracer gas source into the test object 3 and may be of anysuitable type. The gas pressure regulator is arranged to control theoutput pressure from the tracer gas source and may be of any suitabletype.

Furthermore, the second embodiment of the system 1 comprises a base unit10 to which the sniffer probe 4 is connectable by means of a connectionline 11. The connection line 11 is flexible in order to enable movementof the sniffer probe 4 in relation to the base unit 10.

In the second embodiment of the system 1, the base unit 10 comprises avacuum pump 12, which is arranged to provide a vacuum so as to providethat gas is sucked in at the gas inlet orifice 6. Furthermore, the baseunit 10 comprises a tracer gas sensor 13, to which gas is mediated fromthe gas inlet orifice 6 and which is arranged to selectively detect theutilized tracer gas. For example, the tracer gas sensor 13 may be aninfrared gas analyzer, a hydrogen gas sensitive sensor or a massspectrometer. Instead of being positioned in the base unit 10, thetracer gas sensor 13 may alternatively may be positioned within thesniffer probe 4.

In addition, the base unit 10 comprises a tracer gas measuring unit 14,which is arranged to measure and interpret signals from the tracer gassensor 13, and a time measuring unit 15, which is arranged to measurethe time the sniffer tip 5 is positioned within the predetermineddistance interval from the marker 7 during a test. The time measuringunit 15 may further be arranged to either alert the user by a signalwhen the sniffer tip 5 has been positioned within the predetermineddistance interval from the marker 7 during a predetermined time or tointerrupt the test when such time has lapsed.

The base unit 10 comprises further a marker counting unit 16, which isarranged to count the number of leakage testing points tested, and atest result recording unit 17, which is 20 arranged to store testresults, i.e. to store measurements of the amount of tracer gas that hasleaked out of the test object 3 at the leakage testing point 2.Optionally, it may also be arranged to store the measurement time andthe number of leakage testing points tested. In case the markers 7comprise an identity, the identity may be stored together with themeasurement results and the measurement time.

Optionally, the system 1 may further comprise a suction flow generatingunit (not shown) arranged to generate a suction flow from the sniffertip 5 to the tracer gas sensor 13.

Furthermore, the system 1 may further comprise a leak rate limit settingunit (not shown) by which a leak rate limit for a leakage testing pointmay be set, i.e. by which a limit may be set for when the leakage isacceptable or not.

In addition, the system 1 may optionally comprise a fixture for the testobject and a fixture controller (not shown). The fixture for the testobject is arranged to be connected to the test object for filling andremoving gas as well as to seal any other openings not constitutingleakage testing points. The fixture controller is arranged to maneuverthe connections and seals of the fixture. In case the system 1 comprisesa fixture, the marker 7 may either be arranged to be attached on thetest object 3 or on the fixture at the leakage testing point 2.Optionally the fixture may then be provided with a special component,such as e.g. an arm or the like, for holding the marker 7 close to theleakage measurement point 2, i.e. at the leakage testing point 2.

In alternatives to the second embodiment, the system 1 comprises thesniffer probe 4, the marker 7, the marker detector 8 and at leastcomponent from the group of the tracer gas supplying device 9, thevacuum pump 12, the tracer gas sensor 13, the tracer gas measuring unit14, the time measuring device 15, the marker counting unit 16, the testresult recording unit 17, the suction flow generating unit, the leakrate limit setting unit, the fixture and the fixture controller.

FIG. 3 shows a schematic view of a third embodiment of the system 1according to the invention. The third embodiment of the system 1 isdesigned to be utilized in the above described spraying method andcomprises a tracer gas spraying device 18 having a spraying tip 19.Tracer gas is schematically illustrated in FIG. 3 in the form of dots.

As above described, the test object 3 is under vacuum in the sniffingmethod and tracer gas leaking into the test object 3 is detected. Thetracer gas spraying device 18 is arranged to spray tracer gas onto thetest object 3 by means of the spraying tip 19. More specifically, thespraying tip 19 comprises a gas outlet orifice 20 arranged to mediatetracer gas from the interior of the tracer gas spraying device 18 ontothe test object 3. The spraying device 18 may comprise a tracer gassource or may be connectable to a separate tracer gas source. Due to itstracer gas mediating properties, the spraying device 18 is hereindenoted as a tracer gas mediating device.

Furthermore, the tracer gas spraying device 18 is positionable, i.e. itmay be moved in order to position the spraying tip 19 at a certainlocation in relation to the test object 3. The spraying device 18 may bea hand-held unit intended to be manually operated or may be a unitintended to be attached to and manipulated by a robot.

The third embodiment of the system 1 according to the inventioncomprises the marker 7 and the marker detector 8, which corresponds tothe marker 7 and marker detector 8, respectively, in the first andsecond embodiments. The marker 7 may either be arranged to be attachedon the test object 3 or on a fixture close to the leakage testing point.The marker detector 8 may be positioned either on the outside of thespraying device 18 or within the spraying device 18.

The spraying tip 19 is arranged to be positioned within a predetermineddistance interval from the marker 7 during a leak detection test inorder to provide reliable test results. In order to certify a correctpositioning of the spraying tip 19 within the predetermined distanceinterval, the marker detector 8 is arranged to detect the marker 7 whenthe spraying tip 19 is positioned within the predetermined distanceinterval.

FIG. 4 shows a schematic view of a fourth embodiment of the system 1according to the invention, which comprises the tracer gas sprayingdevice 18, the marker 7 and the marker detector 8 of the thirdembodiment of the system 1. However, the fourth embodiment of the system1 comprises further the base unit 10, which is connectable to theinterior of the test object 3 by means of the connection line 11. Thebase unit 10 of the fourth embodiment corresponds to the base unit 10 ofthe second embodiment except for the fact that it is connectable to theinterior of the test object 3 instead of being connectable to thesniffer probe 4 and that it is arranged to detect tracer gas within thetest object 3. Thus, the base unit 10 comprises the vacuum pump 12, thetracer gas sensor 13, the tracer gas measuring unit 14, the timemeasuring unit 15, the marker counting unit 16 and the test resultrecording unit 17. Optionally, the system 1 may further comprise asuction flow generating unit (not shown) arranged to generate a suctionflow from the interior of the test object 3 to the tracer gas sensor 13.In addition, the fourth embodiment of the system 1 may comprise afixture and a fixture controller corresponding to those units in thesecond embodiment. In case the system 1 comprises a fixture, the marker7 may either be arranged to be attached on the test object 3 or on thefixture at the leakage testing point 2. Optionally, the fixture may thenbe provided with a special component, such as e.g. an arm or the like,for holding the marker 7 close to the leakage measurement point 2.

In alternatives to the fourth embodiment, the system 1 comprises thetracer gas spraying device 18, the marker 7, the marker detector 8 andat least one of the vacuum pump 12, the tracer gas sensor 13, the tracergas measuring unit 14, the time measuring device 15, the marker countingunit 16, the test result recording unit 17, the suction flow generatingunit, the fixture and the fixture controller.

Thus, while there have been shown and described and pointed outfundamental novel features of the invention as applied to preferredembodiments thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devices, methodsteps and products illustrated may be made by those skilled in the art.For example, it is expressly intended that all combinations of thoseelements and/or method steps which perform substantially the samefunction in substantially the same way to achieve the same results arewithin the scope of the invention. Moreover, it should be recognizedthat structures and/or elements and/or method steps shown and/ordescribed in connection with any disclosed form or embodiment of theinvention may be incorporated in any other disclosed or described orsuggested form or embodiment as a general matter of design choice. It isthe intention, therefore, to be limited only as indicated by the scopeof the claims appended hereto.

1. A system for detection of a leak at a leakage testing point of a testobject by a tracer gas, the system comprising: a positionable tracer gasmediating unit having a tip; a marker being attachable at said leakagetesting point; and a marker detector being associated with saidpositionable tracer gas mediating unit, whereby said tip of said tracergas mediating unit is arranged to be positioned within a predetermineddistance interval from said marker during a leak detection test, wherebysaid marker detector is arranged to detect said marker when said tip ispositioned within said predetermined distance interval so as to certifya correct positioning of said tip.
 2. The system according to claim 1,wherein said tracer gas mediating unit comprises a sniffer probe havinga sniffer tip, which comprises a gas inlet orifice arranged to mediatetracer gas into the interior of the sniffer probe.
 3. The systemaccording to claim 2, further comprising: at least one component fromthe group of a tracer gas supplying device, a vacuum pump, a tracer gassensor, a tracer gas measuring unit, a time measuring device , a markercounting unit, a test result recording unit, a suction flow generatingunit, a leak rate limit setting unit, a fixture and a fixturecontroller.
 4. The system according to claim 1, wherein the tracer gasmediating unit comprises a tracer gas spraying device having a sprayingtip, which comprises a gas outlet orifice arranged to mediate tracer gasfrom the interior of the spraying device onto the test object.
 5. Thesystem according to claim 4, further comprising: at least one componentfrom the group of a vacuum pump, a tracer gas sensor, a tracer gasmeasuring unit, a time measuring device, a marker counting unit, a testresult recording unit, a suction flow generating unit, a fixture and afixture controller.
 6. The system according to claim 1, wherein saidmarker comprises a radio frequency tag and said marker detectorcomprises a radio frequency tag reader.
 7. The system according to claim6, wherein said marker comprises a radio frequency identification tagand said marker detector comprises a radio frequency identification tagreader.
 8. The system according to claim 1, wherein said markercomprises a light reflecting component and said marker detectorcomprises a light emitting device and a light receiving device.
 9. Thesystem according to claim 1, wherein said marker comprises a magneticink and said marker detector comprises a magnetic ink reader.
 10. Thesystem according to claim 1, wherein said marker is arranged to beattached on the test object.
 11. The system according to claim 1,further comprising: a fixture, wherein said marker is arranged to beattached on the fixture at the leakage testing point.
 12. The systemaccording to claim 1, wherein said tracer gas mediating unit comprises ahand-held unit.
 13. The system according to claim 1, wherein said tracergas mediating unit is arranged to be attached to and manipulated by arobot.